The congressional hearings last week on social media and disinformation ostensibly focused on Russia’s use of advertisements to meddle in American politics. But at their heart, they were about much more: the growth of these technology companies to a scale and power neither the platforms nor Congress really understand.

Representatives from Facebook, Google and Twitter agreed with the assessment of Senator Sheldon Whitehouse, the Democrat from Rhode Island, that the companies have responsibilities beyond simply providing a forum for users to share content. This admission may seem minor, but it represents a sea change in how these companies think of themselves. They are no longer fighting to be seen only as neutral platforms disengaged from the questions raised by the material their users choose to post.

Those who advocate that technology companies do more to combat disinformation and misbehaviour often argue that they should be seen as media organisations with editorial control. But Facebook, Google and Twitter have consistently rejected this idea. While the companies have now accepted some responsibility for the material on their platforms, it is not clear what form they see that responsibility taking or how far it goes. If they are more than neutral platforms yet not publishers, it’s not even clear what they are.

Many of the hearings’ most revealing exchanges put this confusion on full display as members of Congress and technology representatives struggled to understand one another.

At one point, Trey Gowdy, the Republican representative from South Carolina, quizzed Facebook general counsel Colin Stretch: “Do you think the Constitution protects intentionally false statements?”

“We’re trying to provide a platform for authenticity,” Stretch answered, explaining that “on Facebook, our job is not to decide whether content is true or false”. The reason Facebook froze Russian accounts distributing divisive political advertisements, he said, was not that those adverts contained false information but that the accounts were “inauthentic” — fakes.

“For the life of me,” Gowdy said, “I do not understand how a republic is served by provably, intentionally false information.”

The exchange was dizzying. Gowdy posed a question of constitutional law, which controls the Government’s behaviour. Stretch responded by asserting Facebook’s role as a “platform”, not a government, bound by its terms of service, which prohibit fake accounts but take no position on truth or falsehood. Then Gowdy’s closing remark pivoted back to the question of how Facebook shapes American society, as though the company were quasi-governmental.

Other lawmakers expressed astonishment that Facebook stores more information on US citizens than the Federal Government does. They questioned whether the company should understand itself as loyal to the United States or as some kind of amorphous transnational entity.

Underlying all this confusion was a simple question to which no one — neither members of Congress nor the technology representatives — seemed to have an answer: what exactly are these companies?

They are not newspapers but have made themselves into the place where millions of citizens go every day to read news and discuss politics. They are not governments but enjoy enormous authority, reaching across borders and negotiating with governments. They are extraordinarily powerful but have so far evaded significant regulation — although that may change. They are not controlled by the constitutional limitations that bind the US Government and yet have established themselves as the inadvertent custodians of the country’s democracy.

This is how we end up with Senator Marco Rubio, the Republican from Florida, asking the entirely reasonable yet wholly absurd question of whether Russian election-meddling violated Twitter’s terms of service. (According to Twitter’s acting general counsel, Sean Edgett, it did not.) And it is why the exchange between Stretch and Gowdy was so telling. Stretch spoke in the language of Facebook’s terms of service, while the congressman responded in the language of the Federalist Papers.

Precisely because these companies, particularly Facebook, have such vast reach, any meaningful conversation about their influence over elections and the health of the republic has to extend beyond the issue of Russian adverts. As Adam Schiff, the Democratic representative from California, noted, the much larger issue is how powerful social-media companies stoke division by enabling their users to live within curated political worlds, not only disconnecting left from right but providing them separate realities to call home. “Everyone who shows up on Facebook is required to be their authentic self,” Stretch said. Yet rather than allowing us to express our “authentic selves”, Facebook itself shapes our behaviour by showing us what it thinks we are most likely to click on. And if the Russian propaganda was effective, it worked because it resonated with the selves we create in conjunction with Facebook: our ugliest fears and desires, our willingness to set aside truth when it becomes inconvenient. Facebook, Twitter and Google have put that ugliness on the market. This would be bad enough, except the market has also become the new American public square.

Meanwhile, the midterm elections are approaching. All three companies said they were unsatisfied with their response to the 2016 election, but they showed little understanding of what would have constituted a satisfactory response. The only proposed legislation — from Democratic senators Mark Warner, from Virginia, and Amy Klobuchar, from Minnesota — focuses narrowly on mandating transparency for political adverts online. Even if Russia leaves social media alone in 2018, we will still have to deal with ourselves, clicking and scrolling our way to the polls.

•Quinta Jurecic, an associate editor for the Lawfare blog, is serving as a member of The Washington Post editorial board